Polymeric photo active agents

ABSTRACT

The present disclosure is drawn to a polymeric photo active agent which includes diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with a polyether having from 2 to 200 ether groups.

BACKGROUND

Recently, curing of ink by radiation, and in particular ultraviolet (UV)curing, has become popular. UV curable ink can be cured after printingby application of UV light. Typically, UV curable inks include monomersthat form polymers by free radical polymerization. The growing end ofeach polymer chain is a radical that reacts with additional monomers,transferring the radical to the end of the chain as each monomer isadded. A photo initiator can be used to form first radicals to begin thepolymerization process. The photo initiator can be capable of absorbingUV light to generate radicals to react with the monomers.

Two types of photo initiators can be used in UV curable compositions.Type I photo initiators are unimolecular photo initiators that undergo ahemolytic bond cleavage upon absorption of UV light, forming radicals.Type II photo initiators are bimolecular photo initiators. These areused as a system of a photo initiator with a synergist, which cantogether form radicals upon exposure to UV light. Some Type II photoinitiators react by hydrogen abstraction from the synergist to the photoinitiator.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an example of a general scheme of forming a water solublepolymeric TPO compound in accordance with the present disclosure; and

FIG. 2 depicts an example method of preparing a photo curable ink inaccordance with the present disclosure.

DETAILED DESCRIPTION

The inkjet printing industry uses various types of inks, such asoil-based inks, solvent-based (non-aqueous) inks, water-based (aqueous)inks, and solid inks which are melted in preparation for dispensing.Solvent-based inks are fast drying, and as a result, are widely used forindustrial printing. When solvent-based inks containing binders andother ingredients are jetted onto a substrate, the solvent(s) partiallyor fully evaporate from the ink, leaving the binder and otheringredients such as pigment particles on the printed substrate in theform of a dry film. During the drying process, the solvents, which areoften volatile organic compounds (VOC), emit vapors, and therefore, canpollute the environment. The amount of pollution produced can increasegreatly with higher printing speeds or for wide format images wherelarge amounts of ink are deposited onto a substrate. As a result of thisand other concerns, efforts related to preparing inks that areenvironmentally friendly have moved some research in the direction ofwater-based inks. However, radiation curable (or photo curable)water-based ink compositions are noticeably limited among availableoptions due to their specific formulation properties. For example, eventhough one can use dispersions of photo initiators along with adispersant, there can be crystal issues that get introduced at highconcentrations in the ink. Thus, it would be desirable to develop watersoluble and UV-LED reactive photo initiators, including those that mayalso be stable in photo curable ink formulations, have relatively highwater solubility, and/or are chemical stable. In some specific examples,photo initiators (with or without a sensitizer) may also be desirablethat have high reactivity to commercially available UV-LED lights, suchas 395 nm LED lights. Furthermore, because the photo initiatorsdescribed herein can be polymeric, and thus can have improvedperformance with respect to migration in water-based inks, e.g.,migration is minimized.

Accordingly, the present disclosure is drawn to water soluble polymericphoto active agents that can be used as photo initiators, sensitizers,or both. More specifically, the present disclosure is drawn to polymericphoto active agents, including adiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups. In one example, thepolyether includes one of a polyethylene oxide or a polypropylene oxide.In another example, the polyether includes both a polyethylene oxide anda polypropylene oxide. In still other examples, the polyether can alsobe a polyetheramine. For example, the polyetheramine can be a tertiaryamine attached to polyethylene oxide, polypropylene oxide, or acombination of both polyethylene oxide and polypropylene oxide. Inanother example, the polymeric photo active agent can also include asecond diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide that is attachedto the diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide through thepolyether.

In another example, a photo curable ink can include a photo reactivebinder; a polymeric photo active agent includingdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups; a co-photo initiator, asynergist, or combination thereof; a colorant; and a liquid vehicleincluding co-solvent and water. In this example, the polyether caninclude a polyethylene oxide, a polypropylene oxide, or both apolyethylene oxide and a polypropylene oxide. In another example, thepolyether can be part of a polyetheramine. Furthermore, the polymericphoto active agent can also include a seconddiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, wherein thediphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and the seconddiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide are attached together bythe polyether. These photo curable inks can have a pH of 7 to 12, andthe polymeric photo active agent can be stable in the photo curable ink.The photo curable ink can be formulated to be photo curable using UV LEDelectromagnetic radiation. As the photo curable inks include asensitizer or a co-photo initiator, the polymeric photo active agent canact in either capacity. For example, the polymeric photo active agentcan be a sensitizer and the photo curable ink can include the co-photoinitiator. Alternatively, the polymeric photo active agent can act as aphoto initiator and the photo curable ink can include the synergist.

In another example, a method of making a photo curable ink can includemixing a photo reactive binder; a co-photo initiator, a synergist, orcombination thereof; a colorant; and a liquid vehicle includingco-solvent and water with a polymeric photo active agent includingdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups.

In further detail as it relates to the photo active agent, as mentioned,diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) can be modifiedwith a polyether having from 2 to 200 ether groups, as shown in FIG. 1.

There are various structures that can be prepared to solubilize the TPOin water using polyethers. Essentially, the 3-position or the 5-positionof the 2,4,6-trimethyl benzoyl ring portion of the TPO is available formodification with the polyether groups as described herein. In someexamples, the polyether is attached directly to the trimethyl benzoylring, and in other examples, an amine group may be used to attach theTPO to the polyether. Regardless, various examples include thepreparation of polyether-modified TPO. In various examples, TPO can bemodified using Jeffamine® M (Formula I), polymeric TPO can be modifiedusing mono-methylated polyethylene glycol (Formula II), polymeric TPOcan be modified using Jeffamine® D (Formula III), polymeric TPO can bemodified using Jeffamine® XTJ (Formula IV), and polymeric TPO usingpolyethylene glycol (Formula V). Jeffamine® products are available fromHuntsman Corporation of Woodlands, Tex. Notably, Jeffamine® productsused in these examples can include polyethylene glycol and/orpolypropylene glycol. These five examples (I-V) are provided below:

In Formulas I-V above, n can be from 0 to 200 and p can be from 0 to 200m with the proviso that n+p is at least 2.

There are various synthetic methods that can be used to prepare thesecompounds (Formulas I-V). For example, as shown in Scheme 1 below,reaction of commercially available TPO (1) with 3 equivalents ofparaformaldehyde in the presence of AlCl₃ in chloroform at 0° C.,followed by heating at 60° C., gives the corresponding TPO chloride (2).Reaction of 2 equivalents of TPO chloride (2) with Jeffamine® M in thepresence of K₂CO₃ in acetonitrile under reflux gives a polymeric TPObased on Jeffamine® M (Formula I).

Similarly, as shown in Scheme 2, reaction of commercially available TPO(1) with 6 equivalents of paraformaldehyde in the presence of AlCl₃ inchloroform at 0° C., followed by heating at 60° C., gives thecorresponding TPO di-chloride (4). Reaction of TPO di-chloride (4) with2 equiv of mono-methylated polyethylene glycol (5) in the presence ofNaH in THF at 0° C. to room temperature, gives a polymeric TPO based onmono-methylated polyethylene glycol (Formula II).

As shown in Scheme 3, reaction of 4 equivalents of TPO chloride (2) withJeffamine® D (6) in the presence of K₂CO₃ in acetonitrile under refluxgives the desired polymeric TPO based on Jeffamine® D (Formula III).

As shown in Scheme 4, reaction of 2 equivalents of TPO chloride (2) withJeffamine® XTJ (7) in the presence of K₂CO₃ in acetonitrile under refluxgives the desired polymeric TPO based on Jeffamine® XTJ (Formula IV).

As shown in Scheme 5, reaction of 2 equivalents of TPO chloride (2) withpolyethylene glycol (8) in the presence of NaH in THF at 0° C. to roomtemperature, gives a polymeric TPO based on polyethylene glycol (FormulaV).

The present disclosure also extends to photo curable inks, such as UVcurable inks including LED curable inks. In some examples, a photocurable ink can include a photo reactive binder (such as a UV curable orLED curable binder), a polymeric photo active agent, a co-photoinitiator and/or a synergist, a colorant, a co-solvent, and water. Thepolymeric photo active agent can be the PTO modified with a polyetherchain as described herein. In various aspects, the polymeric photoactive agent can act as a photo initiator with the synergist, or it canact as a sensitizer for a co-photo initiator, for example.

In some cases, the photo reactive binder can include a UV or LED curablepolyurethane and hydrophobic radiation-curable monomers. In one example,the UV reactive binder can include a water dispersible (meth)acrylatedpolyurethane, such as NeoRad® R-441 by NeoResins (Avecia). Otherexamples of UV reactive binders can include Ucecoat® 7710, Ucecoat® 7655(available from Cytec), Neorad® R-440, Neorad® R-441, Neorad® R-447,Neorad® R-448 (available from DSM NeoResins), Bayhydrol® UV 2317,Bayhydrol® UV VP LS 2348 (available from Bayer), Lux 430, Lux 399, Lux484 (available from Alberdingk Boley), Laromer® LR 8949, Laromer® LR8983, Laromer® PE 22WN, Laromer® PE 55WN, Laromer® UA 9060 (availablefrom BASF), or combinations thereof.

The polymeric photo active agents of the present disclosure can act as aType I or a Type II photo initiator. Thus, the photo curable ink caninclude a synergist so that the photo initiator and synergist togethercan generate radicals during photo curing, such as with UV curing oreven LED curing processes. In some examples, the synergist can be anamine synergist. The amine synergist can be a tertiary amine compound.In one example, the amine synergist can be a polymeric amine synergistsuch as a derivative of aniline and a polyether amine such as Jeffamine®900. In other examples, the amine synergist can be trimethylamine,triethanolamine, methyldiethanolamine, phenyldiethanolamine,N,N,N′,N′-tetra(hydroxylethyl)ethylenediamine, dimethylaminoethylacrylate, dimethylaminoethyl methacrylate, ethyl dimethylaminobenzoate,or combinations thereof.

In another example, the polymeric photo active agents of the presentdisclosure can act as the primary photo initiator in the photo curableink, or they can act as a sensitizer for another photo initiator.Therefore, the photo curable ink can, in some cases, include a secondphoto initiator in addition to the polymeric photo active agentsdisclosed herein. Examples of radical photo initiators include, by wayof illustration and not limitation, 1-hydroxy-cyclohexylphenylketone,benzophenone, 2,4,6-trimethylbenzo-phenone, 4-methylbenzophenone,diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6trimethylbenzoyl)phosphine oxide,2-hydroxy-2-methyl-1-phenyl-1-propanone, benzyl-dimethyl ketal,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, orcombinations thereof. Non-limiting examples of additional photoinitiators include alpha amino ketone UV photo initiators such as Ciba®Irgacure® 907, Ciba® Irgacure® 369, and Ciba® Irgacure® 379; bisacylphosphine oxide (BAPO) UV photo initiators such as Irgacure® 819,Darocur® 4265, and Darocur® TPO; alpha hydroxy ketone UV photoinitiators such as Irgacure® 184 and Darocur® 1173; including photoinitiators with or without sensitizers such as Darocur® ITX (2-isopropylthioxanthone).

The colorant in the photo curable ink can be a pigment, a dye, or acombination thereof. In some examples, the colorant can be present in anamount from 0.5 wt % to 10 wt % in the photo curable ink. In oneexample, the colorant can be present in an amount from 1 wt % to 5 wt %.In another example, the colorant can be present in an amount from 5 wt %to 10 wt %.

In some examples, the colorant can be a dye. The dye can be nonionic,cationic, anionic, or a mixture of nonionic, cationic, and/or anionicdyes. Specific examples of dyes that can be used include, but are notlimited to, Sulforhodamine B, Acid Blue 113, Acid Blue 29, Acid Red 4,Rose Bengal, Acid Yellow 17, Acid Yellow 29, Acid Yellow 42, AcridineYellow G, Acid Yellow 23, Acid Blue 9, Nitro Blue Tetrazolium ChlorideMonohydrate or Nitro BT, Rhodamine 6G, Rhodamine 123, Rhodamine B,Rhodamine B Isocyanate, Safranine O, Azure B, and Azure B Eosinate,which are available from Sigma-Aldrich Chemical Company (St. Louis,Mo.). Examples of anionic, water-soluble dyes include, but are notlimited to, Direct Yellow 132, Direct Blue 199, Magenta 377 (availablefrom Ilford AG, Switzerland), alone or together with Acid Red 52.Examples of water-insoluble dyes include azo, xanthene, methine,polymethine, and anthraquinone dyes. Specific examples ofwater-insoluble dyes include Orasol® Blue GN, Orasol® Pink, and Orasol®Yellow dyes available from Ciba-Geigy Corp. Black dyes may include, butare not limited to, Direct Black 154, Direct Black 168, Fast Black 2,Direct Black 171, Direct Black 19, Acid Black 1, Acid Black 191, MobayBlack SP, and Acid Black 2.

In other examples, the colorant can be a pigment. The pigment can beself-dispersed with a polymer, oligomer, or small molecule; or can bedispersed with a separate dispersant. Suitable pigments include, but arenot limited to, the following pigments available from BASF: Paliogen®Orange, Heliogen® Blue L 6901F, Heliogen® Blue NBD 7010, Heliogen® BlueK 7090, Heliogen® Blue L 7101F, Paliogen® Blue L 6470, Heliogen® Green K8683, and Heliogen® Green L 9140. The following black pigments areavailable from Cabot: Monarch® 1400, Monarch® 1300, Monarch® 1100,Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800, and Monarch®700. The following pigments are available from CIBA: Chromophtal® Yellow3G, Chromophtal® Yellow GR, Chromophtal® Yellow 8G, Igrazin® Yellow 5GT,Igralite® Rubine 4BL, Monastral® Magenta, Monastral® Scarlet, Monastral®Violet R, Monastral® Red B, and Monastral® Violet Maroon B. Thefollowing pigments are available from Degussa: Printex® U, Printex® V,Printex® 140U, Printex® 140V, Color Black FW 200, Color Black FW 2,Color Black FW 2V, Color Black FW 1, Color Black FW 18, Color Black S160, Color Black S 170, Special Black 6, Special Black 5, Special Black4A, and Special Black 4. The following pigment is available from DuPont:Tipure® R-101. The following pigments are available from Heubach:Dalamar® Yellow YT-858-D and Heucophthal Blue G XBT-583D. The followingpigments are available from Clariant: Permanent Yellow GR, PermanentYellow G, Permanent Yellow DHG, Permanent Yellow NCG-71, PermanentYellow GG, Hansa Yellow RA, Hansa Brilliant Yellow 5GX-02, HansaYellow-X, Novoperm® Yellow HR, Novoperm® Yellow FGL, Hansa BrilliantYellow 10GX, Permanent Yellow G3R-01, Hostaperm® Yellow H4G, Hostaperm®Yellow H3G, Hostaperm® Orange GR, Hostaperm® Scarlet GO, and PermanentRubine F6B. The following pigments are available from Mobay: Quindo®Magenta, Indofast® Brilliant Scarlet, Quindo® Red R6700, Quindo® RedR6713, and Indofast® Violet. The following pigments are available fromSun Chemical: L74-1357 Yellow, L75-1331 Yellow, and L75-2577 Yellow. Thefollowing pigments are available from Columbian: Raven® 7000, Raven®5750, Raven® 5250, Raven® 5000, and Raven® 3500. The following pigmentis available from Sun Chemical: LHD9303 Black. Any other pigment and/ordye can be used that is useful in modifying the color of the UV curableink. Additionally, the colorant can include a white pigment such astitanium dioxide, or other inorganic pigments such as zinc oxide andiron oxide.

The components of the photo curable ink can be selected to give the inkgood ink jetting performance. Besides the photo curable binder, photoreactive polymeric photo active agents, and the colorant, the photocurable ink can also include a liquid vehicle. Liquid vehicleformulations that can be used in the photo curable ink can include waterand one or more co-solvents present in total at from 1 wt % to 50 wt %,depending on the jetting architecture. Further, one or more non-ionic,cationic, and/or anionic surfactant can be present, ranging from 0.01 wt% to 20 wt %. In one example, the surfactant can be present in an amountfrom 5 wt % to 20 wt %. The liquid vehicle can also include dispersantsin an amount from 5 wt % to 20 wt %. The balance of the formulation canbe purified water, or other vehicle components such as biocides,viscosity modifiers, materials for pH adjustment, sequestering agents,preservatives, or the like. In one example, the liquid vehicle can bepredominantly water, e.g., more than 50 wt % water.

Classes of co-solvents that can be used can include organic co-solventsincluding aliphatic alcohols, aromatic alcohols, diols, glycol ethers,polyglycol ethers, caprolactams, formamides, acetamides, and long chainalcohols. Examples of such compounds include primary aliphatic alcohols,secondary aliphatic alcohols, 1,2-alcohols, 1,3-alcohols, 1,5-alcohols,ethylene glycol alkyl ethers, propylene glycol alkyl ethers, higherhomologs (C₆-C₁₂) of polyethylene glycol alkyl ethers, N-alkylcaprolactams, unsubstituted caprolactams, both substituted andunsubstituted formamides, both substituted and unsubstituted acetamides,and the like. Specific examples of solvents that can be used include,but are not limited to, 2-pyrrolidinone, N-methylpyrrolidone,2-hydroxyethyl-2-pyrrolidone, 2-methyl-1,3-propanediol, tetraethyleneglycol, 1,6-hexanediol, 1,5-hexanediol and 1,5-pentanediol.

One or more surfactants can also be used, such as alkyl polyethyleneoxides, alkyl phenyl polyethylene oxides, polyethylene oxide blockcopolymers, acetylenic polyethylene oxides, polyethylene oxide(di)esters, polyethylene oxide amines, protonated polyethylene oxideamines, protonated polyethylene oxide amides, dimethicone copolyols,substituted amine oxides, and the like. The amount of surfactant addedto the formulation of this disclosure may range from 0.01 wt % to 20 wt%. Suitable surfactants can include, but are not limited to, liponicesters such as Tergitol™ 15-S-12, Tergitol™ 15-S-7 available from DowChemical Company, LEG-1 and LEG-7; Triton™ X-100; Triton™ X-405available from Dow Chemical Company; LEG-1, and sodium dodecylsulfate.

Consistent with the formulation of this disclosure, various otheradditives can be employed to optimize the properties of the inkcomposition for specific applications. Examples of these additives arethose added to inhibit the growth of harmful microorganisms. Theseadditives may be biocides, fungicides, and other microbial agents, whichare routinely used in ink formulations. Examples of suitable microbialagents include, but are not limited to, NUOSEPT® (Nudex, Inc.),UCARCIDE™ (Union carbide Corp.), VANCIDE® (R.T. Vanderbilt Co.), PROXEL®(ICI America), and combinations thereof.

Sequestering agents, such as EDTA (ethylene diamine tetra acetic acid),may be included to eliminate the deleterious effects of heavy metalimpurities, and buffer solutions may be used to control the pH of theink. From 0.01 wt % to 2 wt %, for example, can be used. Viscositymodifiers and buffers may also be present, as well as other additives tomodify properties of the ink as desired. Such additives can be presentat from 0.01 wt % to 20 wt %.

Table 1 shows the composition of an example of a photo curable ink,e.g., UV LED curable ink, formulation in accordance with the presentdisclosure. The ink can be formulated by mixing these ingredients or byother formulations. The pH of the ink can then be adjusted. In oneexample, the ingredients can be stirred for 30 minutes and then aqueouspotassium hydroxide can be added to adjust the pH to 7 to 12, or inother examples, from 8 to 10, or about 8.5. It is noted that thoughwater concentrations are listed as “balance,” it is understood that thebalance of components could included other liquid vehicle components orminor amounts of solids often present in inkjet ink compositions.

TABLE 1 Component Weight Percent Photo reactive binder  1-20% (UVreactive polymer) Polymeric photo active agent 0.15-5%   (sensitizer orphoto initiator) Co-photo initiator *0-10% Synergist *0-5%  Surfactant 0-20% Anti-kogation agent 0-5% Pigment 0.5-10%  Organic Co-solvent0.1-50%  Water remainder *As noted, when the polymeric photo activeagent is included as a sensitizer, the co-photo initiator is at greaterthan 0%. When the polymeric photo active agent is included as a photoinitiator, the synergist is at greater than 0%.All three components can likewise be present, i.e. the polymeric photoactive agent, the co-photo initiator, and the synergist.

The photo curable ink can be used to print on a broad selection ofsubstrates including untreated plastics, flexible as well as rigid,porous substrates such as paper, cardboard, foam board, textile, andothers. The ink has a good adhesion on a variety of substrates. Thephoto curable ink also has a good viscosity, enabling good printingperformances and enabling the ability to formulate inks suitable forinkjet applications. In some examples, the ink can be formulated forthermal inkjet printing. The photo curable ink composition of thepresent disclosure provides for high printing speed and is very wellsuited for use in digital inkjet printing.

The polymeric photo active agents of the present disclosure can bestable in aqueous environments at pH from 7 to 12 or higher. Thus, thephoto curable ink can be formulated to have a pH from 7 to 12 or higher.In some examples, the photo curable ink can have a pH of 8 or higher,e.g., 8 to 12 or 8 to 10. In one specific example, the photo curable inkcan have a pH of about 8.5.

The polymeric photo active agent can exhibit less migration in cured inkcompared with small molecule photo initiators. The photo curable binderin the ink can include polymers or monomers that polymerize orcross-link during the curing process. As the binder cures, the polymericphoto active agent can become locked into the cured binder due to thelong polyether chain of the polymeric photo active agent. Therefore, thephoto curable ink can be formulated so that there is little or nomigration of the polymeric photo active agent in the ink after curing.

As mentioned, the present disclosure also extends to a method of makinga photo curable ink, as shown generally at FIG. 2. The method includesmixing 210 a photo reactive binder; a co-photo initiator, a synergist,or combination thereof; a colorant; and a liquid vehicle includingco-solvent and water with a polymeric photo active agent includingdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups. The photo curable ink canbe UV curable, and in one specific example, UV LED curable. In oneexample, the method can also include adjusting the pH of the ink to befrom 7 to 12. In another example, the method can include adjusting thepH of the ink from 8 to 10.

It is to be understood that this disclosure is not limited to theparticular process steps and materials disclosed herein because suchprocess steps and materials may vary somewhat. It is also to beunderstood that the terminology used herein is used for the purpose ofdescribing particular examples only. The terms are not intended to belimiting because the scope of the present disclosure is intended to belimited only by the appended claims and equivalents thereof.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used herein, “polymeric photo active agent” refers to materials thatparticipate in the initiation of photo polymerization, particularlymaterials that act as a photo initiator or a sensitizer for a photoinitiator. The polymeric photo active agents disclosed herein can beused either as a photo initiator or as a sensitizer for another photoinitiator. In some systems, the polymeric photo active agent can act asboth a photo initiator and a sensitizer.

As used herein, “UV curable” refers to compositions that can be cured byexposure to ultraviolet light from any UV source such as a mercury vaporlamp, UV LED source, or the like. Mercury vapor lamps emit highintensity light at wavelengths from 240 nm to 270 nm and 350 nm to 380nm. There are also ultraviolet LEDs available at 365 nm and 395 nmwavelengths, among others. “LED curable” refers to compositions that canbe cured by ultraviolet light from an ultraviolet source, such as anUltraviolet LED (or UV LED) which emits light at a specific wavelength.The term “photo curable” refers generally to compositions that can becured by exposure to light from any wavelength suitable for thecomposition being cured. Typically, the photo curable composition willbe UV curable, and in some cases UV LED curable.

As used herein, “liquid vehicle” or “ink vehicle” refers to a liquidfluid in which colorant is placed to form an ink. A wide variety of inkvehicles may be used with the systems and methods of the presentdisclosure. Such ink vehicles may include a mixture of a variety ofdifferent agents, including, surfactants, solvents, co-solvents,anti-kogation agents, buffers, biocides, sequestering agents, viscositymodifiers, surface-active agents, water, etc.

As used herein, “colorant” can include dyes and/or pigments.

As used herein, “dye” refers to compounds or molecules that absorbelectromagnetic radiation or certain wavelengths thereof. Dyes canimpart a visible color to an ink if the dyes absorb wavelengths in thevisible spectrum.

As used herein, “pigment” generally includes pigment colorants, magneticparticles, aluminas, silicas, and/or other ceramics, organo-metallics orother opaque particles, whether or not such particulates impart color.Thus, though the present description primarily exemplifies the use ofpigment colorants, the term “pigment” can be used more generally todescribe not only pigment colorants, but other pigments such asorganometallics, ferrites, ceramics, etc. In one specific example,however, the pigment is a pigment colorant.

As used herein, “ink-jetting” or “jetting” refers to compositions thatare ejected from jetting architecture, such as ink-jet architecture.Ink-jet architecture can include thermal or piezo architecture.Additionally, such architecture can be configured to print varying dropsizes such as less than 10 picoliters, less than 20 picoliters, lessthan 30 picoliters, less than 40 picoliters, less than 50 picoliters,etc.

As used herein, the term “substantial” or “substantially” when used inreference to a quantity or amount of a material, or a specificcharacteristic thereof, refers to an amount that is sufficient toprovide an effect that the material or characteristic was intended toprovide. The exact degree of deviation allowable may in some casesdepend on the specific context.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint. The degree offlexibility of this term can be dictated by the particular variable anddetermined based on the associated description herein.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range is explicitly recited. As an illustration,a numerical range of “about 1 wt % to about 5 wt %” should beinterpreted to include not only the explicitly recited values of about 1wt % to about 5 wt %, but also the individual values and sub-rangeswithin the indicated range. Thus, included in this numerical range areindividual values such as 2, 3.5, and 4 and sub-ranges such as from 1-3,from 2-4, and from 3-5, etc. This same principle applies to rangesreciting only one numerical value. Furthermore, such an interpretationshould apply regardless of the breadth of the range or thecharacteristics being described.

EXAMPLES

The following illustrates several examples of the present disclosure.However, it is to be understood that the following are only illustrativeof the application of the principles of the present disclosure. Numerousmodifications and alternative compositions, methods, and systems may bedevised without departing from the spirit and scope of the presentdisclosure. The appended claims are intended to cover such modificationsand arrangements.

Example 1—Synthesis of TPO Chloride (2)

A mixture of 5.0 grams (14.3 mmol) of commercially available TPO (1) in100 mL of chloroform was cooled to 0° C. under N₂ and mechanicalstirring was added portion-wise AlCl₃ (12.0 grams, 85.8 mmol) andparaformaldehyde (1.3 grams, 43 mmol). After the completion of theaddition, the mixture was heated to 60° C. for 6 hours. The reactionmixture was cooled to room temperature and poured into ice-water. Themixture was extracted with dichloromethane (3×100 mL). The combinedorganic layers were washed by water, brine and then dried over sodiumsulfate. Evaporation of solvent gave a residue, which was furtherpurified by flash chromatography using hexanes/ethyl acetate (100%hexanes to 50% hexanes in ethyl acetate) as eluents, giving rise to 3.7grams (65%) of TPO chloride (2), as shown in Schemes 1, 3, 4, and 5.

Example 2—Synthesis of TPO Di-Chloride (4)

A mixture of 5.0 grams (14.3 mmol) of commercially available TPO (1) in100 mL of chloroform was cooled to 0° C. under N₂ and mechanicalstirring was added portion-wise AlCl₃ (12.0 grams, 85.8 mmol) andparaformaldehyde (2.6 grams, 86 mmol). After the completion of theaddition, the mixture was heated to 60° C. for 12 hours. Then, thereaction mixture was cooled to room temperature and poured intoice-water. The mixture was extracted with dichloromethane (3×100 mL).The combined organic layers were washed by water, brine and then driedover sodium sulfate. Evaporation of solvent gave a residue, which wasfurther purified by flash chromatography using hexanes/ethyl acetate(100% hexanes to 50% hexanes in ethyl acetate) as eluents, giving riseto 3.8 grams (60%) of TPO-dichloride (4), as shown in Scheme 2.

Example 3—Synthesis of Polymeric TPO Based on Jeffamine® D (Formula III)

To a solution of TPO chloride (2) (15.88 grams, 40 mmol) in 150 mL ofacetonitrile and 50 mL of THF was added potassium carbonate (5.52 grams,40 mmol). To the above mixture was added a solution of Jeffamine® ED-900(6) (9.0 grams, 10 mmol) in 50 mL of THF. After the completion of theaddition, the reaction mixture was stirred under reflux for 24 hours.Then the reaction mixture was cooled to room temperature. The solid wasfiltered off by filtration and washed with ethyl acetate. The combinedorganic layers were washed by water, brine and then dried over sodiumsulfate. Evaporation of solvent gave a residue, which was furtherpurified by flash chromatography using hexanes/ethyl acetate (100%hexanes to 50% hexanes in ethyl acetate) as eluents, giving rise to20.15 grams (85%) of the polymeric TPO of Formula III.

Example 4—Synthesis of polymeric TPO based on Mono-MethylatedPolyethylene Glycol (Formula II)

To a solution of mono-methylated polyethylene glycol (5) (1.65 g, 2.2mmol) in 25 mL of THF was added potassium tert-butoxide (300 mg, 2.65mmol). The resulting mixture was stirred at 50° C. for 2 hours. Aftercooling to room temperature, this mixture was added dropwise to asolution of TPO di-chloride (4) (445 mg, 1.0 mmol) in 25 mL of THF at 0°C. under N₂ atmosphere. The resulting mixture was allowed to stir at 50°C. for an additional 3 hours. The reaction mixture was cooled to roomtemperature and poured into ice-water. The mixture was extracted withdichloromethane (3×100 mL). The combined organic layers were washed bywater, brine and then dried over sodium sulfate. Evaporation of solventgave a residue, which was further purified by flash chromatography usinghexanes/ethyl acetate (100% hexanes to 50% hexanes in ethyl acetate) aseluents, giving rise to 1.4 grams (75%) of the polymeric TPO based onmono-methylated polyethylene glycol of Formula II.

Example 5—Photo Curable Ink 1

A photo (UV LED) curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 1.

TABLE 1 Component Weight Percent UV reactive binder  15% Irgacure ® 8190.3% (co-photo initiator from BASF) Thioxanthone derivative of PEG-6000.5% (sensitizer) Polymeric TPO (Formula I photo initiator) 0.5% LEG-1(surfactant)   1% Surfynol ® CT-211   1% (surfactant from Air Products)Crodafos ® N3 (anti-kogation agent from 0.5% Croda Inc.) Pigments 2.5%2-hydroxyethyl-2-pyrrolidone (co-solvent)  10% Water 69.2% 

Example 6—Photo Curable Ink 2

A photo curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 2.

TABLE 2 Component Weight Percent UV reactive binder   5% Thioxanthonederivative of PEG-600 0.25%  (Sensitizer) Polymeric TPO (Formula IIphoto initiator) 0.5% LEG-1 (surfactant)   1% Surfynol ® CT-211 0.5%(surfactant from Air Products) Crodafos ® N3 0.5% (anti-kogation agentfrom Croda Inc.) Pigments   3% 2-hydroxyethyl-2-pyrrolidone (co-solvent) 10% Water 79.15% 

Example 7—Photo Curable Ink 3

A photo curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 3.

TABLE 3 Component Weight Percent UV reactive binder  10% Thioxanthonederivative of PEG-600 0.25%  (Sensitizer) Polymeric TPO (Formula IIIphoto initiator) 0.5% LEG-1 (surfactant)   1% Surfynol ® CT-211 0.5%(surfactant from Air Products) Crodafose ® N3 0.5% (anti-kogation agentfrom Croda Inc.) Pigments   3% 2-hydroxyethyl-2-pyrrolidone (co-solvent) 10% Water 74.15% 

Example 8—Photo Curable Ink 4

A photo (UV LED) curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 4.

TABLE 4 Component Weight Percent UV reactive binder  15% Irgacure ® 8190.3% (co-photo initiator from BASF) Thioxanthone derivative of PEG-6000.5% (Sensitizer) Polymeric TPO   1% (Formula IV photo initiator) LEG-1(surfactant)   1% Surfynol ® CT-211   1% (surfactant from Air Products)Crodafos ® N3 0.5% (anti-kogation agent from Croda Inc.) Pigments 2.5%2-hydroxyethyl-2-pyrrolidone (co-solvent)  10% Water 68.7% 

Example 9—Photo Curable Ink 5

A photo (UV LED) curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 5.

TABLE 5 Component Weight Percent UV reactive binder  15% Irgacure ® 819(co-photo initiator from 0.3% BASF) Thioxanthone derivative of PEG-6000.5% (Sensitizer) Polymeric TPO (Formula V photo initiator)   3% LEG-1(surfactant)   1% Surfynol ® CT-211   1% (surfactant from Air Products)Crodafos ® N3 0.5% (anti-kogation agent from Croda Inc.) Pigments 2.5%2-hydroxyethyl-2-pyrrolidone (co-solvent)  10% Water 66.7% 

Example 10—Photo Curable Ink 6

A photo (UV LED) curable inkjet ink is prepared by mixing the followingcomponents as shown in Table 6.

TABLE 6 Component Weight Percent UV reactive binder  15% Irgacure ® 8190.3% (co-photo initiator from BASF) Thioxanthone derivative of PEG-6000.5% (Sensitizer) Polymeric TPO (Formula V photo initiator)   5% LEG-1(surfactant)   1% Surfynol ® CT-211 (surfactant from Air   1% Products)Crodafos ® N3 0.5% (anti-kogation agent from Croda Inc.) Pigments 2.5%2-hydroxyethyl-2-pyrrolidone (co-solvent)  10% Water 64.7% 

Example 11—Preparation of Photo Curable Ink 1

Photo Curable Ink 1 was prepared in accordance with the following steps.Notably, Photo Curable Inks 2-6 can be prepared using similar steps. Asa first batch, a UV reactive polyurethane dispersion (UV reactivebinder) was mixed with a minor portion of the total water (less thanabout 30 wt %) and the Irgacure 819 (co-photo initiator) at 60° C. for 5minutes. As a second batch, 2-hydroxyethyl-2-pyrrolidone (co-solvent)was mixed with a larger portion of the total water content (less thanabout 70 wt %) and Crodafos® N3A, CT211, and LEG-1. The second batch wasneutralized to a pH of 7.5 with KOH solution. The first batch and thesecond batch were then combined. Next, a thioxanthone derivative ofPEG-600 (sensitizer) and polymeric TPO (photo initiator) were added andmixed well until they dissolved into mixture. The black pigmentdispersion was then added to the admixture and the pH was adjusted to8.5 using KOH solution. Notably, some additional water content was addedduring subsequent steps after combing the first and second batch,resulting in the water content listed in Table 1.

A print durability test was then conducted using Photo Curable Ink 1, asfollows:

-   -   Sample Preparation    -   1. The Photo Curable Ink was filled into thermal inkjet pen.    -   2. Fixer was printed from a different pen right before the ink        was printed. The fixer formulation was a solution of calcium        propionate, calcium nitrate tetrahydrate, Surfynol® SEF,        tetraethylene glycol, and water.    -   3. Two paper substrates were evaluated:        -   a. Offset coated paper—Sterling® Ultra Gloss (SUG), and        -   b. White Top coated Kraft Liner—RockTenn® 1 (RT1).    -   4. The ink was immediately dried using hot air blower for 5        seconds at 375° F.    -   5. The dried ink was then immediately cured at a speed of 100        feet per minute using a 16 W/cm² LED 395 nm wavelength (from        Phoseon).    -   Durability Measurements    -   1. Wet Rub Test        -   a. This test was performed after a pre-defined time period            after printing and curing. For SUG it was performed 24 hours            after printing, and for RT1 it was preformed 72 hours after            printing.        -   b. A taber test tool was used with Crockmeier cloth attached            to the tip.        -   c. The weight load was 350 gram.        -   d. One (1) cycle was used for SUG, and two (2) cycles was            used for RT1.        -   e. The solution was Windex®;        -   f. For the Wet Rub Test, the delta optical density (ΔOD) was            measured before and after the rub; and        -   g. In this test, the lower the ΔOD, the better the            durability.        -   h. A ΔOD<0.15 is considered to be a good score.    -   2. Immediate Rub Test        -   a. Hand held rubbing tool was used to assess the smearing of            dried and cured ink immediately after printing;        -   b. The tool used was fit with a rubber tip that when pushed            down applied a constant pressure of 6 to 7 lbs;        -   c. For the Immediate Rub Test, the delta optical density            (ΔOD) was measured before and after the rub.        -   d. In this test, the lower the ΔOD, the better the            durability.        -   e. A ΔOD<0.15 is considered a good score.

The Results for the Wet Rub Test and the Immediate Rub Test are providedin Table 7. Notably, the black Photo Curable Ink was printed asdescribed and tested both with and without curing on both papers (SUGand RT1).

TABLE 7 With Curing Without Curing Wet Rub Immediate Rub Wet RubImmediate Rub Paper (ΔOD) (ΔOD) (ΔOD) (ΔOD) SUG 0.12 0.11 1.89 0.89 RTI0.09 0.05 1.45 0.75

As can be seen in Table 7 above, the black Photo Curable Ink exhibitedsignificantly better wet rub and immediate rub resistance after curing.The initial OD was 2.02 and 1.63 on SUG and RT1, respectively, andtherefore a ΔOD of 0.12, for example, indicates that after rubbing theprint, only 0.12 OD units were lost from the initial 2.02 ODmeasurement. Conversely, without curing, a ΔOD of 1.89 means that thatthe ink lost significant OD units from the initial 2.02 OD measurement.The durability improvement by curing is evident in both Wet Rub andImmediate Rub measurements, suggesting that the polymeric TPO basedphoto initiator package efficiently participated in the curing andcrosslinking of the Photo Curable Ink.

While the present technology has been described with reference tocertain examples, those skilled in the art will appreciate that variousmodifications, changes, omissions, and substitutions can be made withoutdeparting from the spirit of the disclosure. It is intended, therefore,that the disclosure be limited only by the scope of the followingclaims.

What is claimed is:
 1. A polymeric photo active agent, comprisingdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups.
 2. The polymeric photoactive agent of claim 1, wherein the polyether includes one of apolyethylene oxide or a polypropylene oxide.
 3. The polymeric photoactive agent of claim 1, wherein the polyether includes both apolyethylene oxide and a polypropylene oxide.
 4. The polymeric photoactive agent of claim 1, wherein the polyether is also a polyetheramine.5. The polymeric photo active agent of claim 4, wherein thepolyetheramine is a tertiary amine attached to polyethylene oxide,polypropylenene oxide, or a combination of both polyethylene oxide andpolypropylene oxide.
 6. The polymeric photo active agent of claim 1,comprising a second diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide,wherein the diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and thesecond diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide are attachedtogether by the polyether.
 7. The polymeric photo active agent of claim1, having one of the following structures:

wherein n is from 0 to 200 and p is from 0 to 200 with the proviso thatn+p is at least
 2. 8. A photo curable ink, comprising: a photo reactivebinder; a polymeric photo active agent comprisingdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified with apolyether having from 2 to 200 ether groups; a co-photo initiator, asynergist, or combination thereof; a colorant; and a liquid vehicleincluding co-solvent and water.
 9. The photo curable ink of claim 8,wherein the polyether includes a polyethylene oxide, a polypropyleneoxide, or both a polyethylene oxide and a polypropylene oxide.
 10. Thephoto curable ink of claim 9, wherein the polyether is also apolyetheramine.
 11. The photo curable ink of claim 8, wherein thepolymeric photo active agent includes a seconddiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, wherein thediphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and the seconddiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide are attached together bythe polyether.
 12. The photo curable ink of claim 8, wherein the photocurable ink has a pH of 7 to 12, wherein the polymeric photo activeagent is stable in the photo curable ink, and wherein the photo curableink is photo curable using UV LED electromagnetic radiation.
 13. Thephoto curable ink of claim 8, wherein the polymeric photo active agentis a sensitizer and the photo curable ink includes the co-photoinitiator.
 14. The photo curable ink of claim 8, wherein the polymericphoto active agent is a photo initiator and the photo curable inkincludes the synergist.
 15. A method of making a photo curable inkcomprising mixing a photo reactive binder; a co-photo initiator, asynergist, or combination thereof; a colorant; and a liquid vehicleincluding co-solvent and water with a polymeric photo active agentcomprising diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide modified witha polyether having from 2 to 200 ether groups.
 16. The polymeric photoactive agent of claim 1, wherein the polyether is bonded to a carbon inthe 3-position or the 5-position of the 2,4,6-trimethyl benzoyl ring.17. The polymeric photo active agent of claim 1, having one of thefollowing structures:

where n is from 0 to 200 and p is from 0 to 200 with the proviso thatn+p is at least 2.